If your sister is having low platelet count then the cause needs to be ascertained. Treatment of the cause will help the platelet counts come back to normal. Also she has to get her blood levels for platelets checked at regular intervals to check any further drop in the platelet counts. She should discontinue any drugs that can cause low platelet count, including heparin. Also she can talk to her doctor about taking steroids or intravenous immunoglobulins (IVIG) or a platelet transfusion.
If the symptoms persist then please get it evaluated from a doctor.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.